Method of making filters



Oct. 27, 1942. .c. HARDY I 230G382 METHOD OFMAKINGVFILTERS Original Filed April 2, 1941 Patented Oct. 27, 1942 METHOD OF MAKING FILTERS Charles L. Hardy, Waban, Mass, assignor to Joseph T. Ryerson & Son, Inc, Chicago, Ill., a v corporation of Delaware Original application April 2, 1941, 'Serial No.

386,433. Divided and this application November 17, 1941, Serial No. 419,417

6 Claims.

This invention pertains to filters designed to clean and/or to defuse a fluid and relates more particularly to improvements in the method of making such filters,the present application being a division of my copending application are not substantially affected by temperature or Serial No. 386,433, filed April 2, 1941, the specific other extreme conditions to which the filter is embodiment here chosen for illustration conexposed during use. Other and further objects cerning the manufacture of a cylindrical filter and advantages of the invention will be pointed through which steam is passed on its way to a out hereafter in the following more detailed deturbine. scriptio'n and byreference to the accompanying Steam filters for turbines are subjected to exdrawing, wherein: tremely trying conditions in use. In recent steam Fig. 1 is a vertical section showing the imengineering practice the tendency has been to proved filter of the present invention installed increase steam pressures and temperatures until in a casing; at the present time pressures exceeding 1800 5 Fig. 2 is a section substantially on the line pounds per square inch and temperatures of the 2-2 of Fig. 1 but omitting the casing; order of 1000 F. are in use. Under such condi- Fig. 3 is a fragmentary plan view showing a tions the velocity of flow through the interstices length of wire useful in making the improved of the filter is very high and stresses are set up screen; which tend to distort and rapidly to erode the Fig. 4 is a fragmentary p View Showing a filter. Moreover, the great variation in temperpiece of such wire bent to constitute a portion ature between the cold and the operating condiof one turn of a helical coil; tions, coupled with such mechanical stresses, Fig. 5 is a fragmentary side elevation of such makes the use of solder or even welded joints a helical coil made from wire of the kind shown between the constituent parts of the filter unin Fig.3; reliable and impracticable. Attempts have here- Fig. 6 is a fragmentary elevation of a mandrel tofore been made to form cylindrical filters of useful in making the improved filter; this kind by rolling a sheet of woven wire filter Fig. 7 is a plan view ofthe mandrel of Fig. 6; material to a cylindrical curvature and then Fig. 8 is a fragmentary enlarged end view of welding its longitudinal edges together, but as the mandrel of Fig. 6 illustrating one step in just above stated, a joint so formed is unreliable the improved method of making filters; under the conditions of use so that filters made Fig. 9 is a fragmentary horizontal section in this way have proven unsatisfactory. showing a cylindrical screen fabric in accord- Screens or filters of this kind must be rigidly ance with the present invention and to larger and reliably supported and for this purpose it is scale than Fig. 2; and desirable to attach each'end of the cylinder of Fig. 10 is a fragmentary 'diametrical section screen material to a rigid supporting ring which showing details of one of the end rings of the not only stifiens the screen material and profilter prior to its assembly with the screen mavides a finish for its ends, but also furnishes terial. convenient means for centering the screen in the 40 Referring to the drawing and in particular to chamber in which it is housed and for rigidly Fig. 3, the numeral I designates a length of wire attaching it to the wall of such chamber or other useful in forming certain elements of the screen appropriate support, but diificulty has also been structure. This wire is of a corrosion-resistant experienced in providing a permanent union beand preferably erosion-resistant material, for tween the screen and its supporting ring. example, stainless steel, bronze, or the like, such One principal object of the present invention material being stiilly resilient but capable of being is to provide a novel method of making 'forampermanently deformed by the application of inous screen material in seamless cylindrical appropriate pressure. Wire of 0.092 inch diamform wherein the assembled elements are so eter has been found useful for the purpose, al-

mechanically united that the screen material is capable of withstanding all of the conditions of use without substantial distortion or variation in the mesh size, although made of a material which is extremely hard or otherwise erosion and corrosion resistant. A further object is to provide a novel method of substantially assembling a cylindrical seamless filter with rigid annuli so mechanically united to the opposite ends of the cylinder of screen material that the connections though it is to be understood that the diameter of the Wire may be varied in accordance with circumstances and in particular with reference to the size of the screen structure and the size of mesh. Wire of the diameter just specifically mentioned is well suited to the making of a screen of No. 5 mesh and of a diameter of the order of 11 inches, and a length of the order of 18 inches.

Having provided wire of the desired characteristics and size, the first step in the operation of making the filter herein disclosed is to crimp this wire transversely, as shown in Fig. 3, in a manner well known in the wire-working art, so as to provide the wire with a series of indentations 2 intervening between successive crests l and IP. In order to emphasize the principle of the invention, these indentations 2 are shown in Figs. 3, 4 and 8 as of a depth substantially equaling the diameter of the wire so that the distance between parallel lines 3 and 4, tangent to the respective crests l and l at opposite sides of the wire, would be approximately twice the diameter of the wire, the distance between the lines 3 and 4 thus substantially equaling the thickness of the wall of the completed screen. In actual practice these indentations or recesses 2 would ordinarily be less in depth than the diameter of the wire.

' Having provided this crimped wire, a lengthis cut'therefrom suflicient to' form a helix whose several turns will constitute the wefts of the proposed for'aminous woven screen fabric, this helix extending from one end to the other of the screen without break. While a single helix may thus be employed to constitute the entire weft or filling of the woven structure, it is contemplated that several helices may be employed with their turns intercalated, thus permitting the use of helices of a' steeper pitch if that should be desired, without' thereby unduly varying the size of mesh. 'Havi'ngprovided thislength of crimped wire, 'it is then coiled in any desired way to form the helix 5 (Fig. 5) having successive turns 6. 6 6 etc., longitudinally spaced apart in accordance with the desired size of mesh.

From thecrimped wire there are also cut substantially straight lengths 11 designed to form warp strands each of a length substantially equaling the desired length of the finished filter. A substantial number of these lengths 1 of the crimped wire is provided and there is also provided a number'of'warp lengths 8 (Fig. 1) of straight uncrimped wire, suchwire preferably being identical'with that employed in preparing thecrimped wire.

In assembling the helix5 with the warp lengths 1' and 8 to form woven" structure, it is convenient to employ a mandrel or similar support, such as shown for example in Figs. 6 and 7-. As here illustrated, this mandrel is a substantially cylindrical shell of stiff but somewhat resilient materiaLthe outer surface of this mandrel preferably being provided with a helical groove I having the pitch which it is desired that the helical coil shall have in the completed filter. The mandrel 9 'also has at one or more points a longitudinal ap or channelll. In the instance illustrated, wherein this mandrel 9 is a hollow cylinder, the channel H is merely an opening or longitudinal slot through the thickness of the wall of the mandrel. On the other hand, if a multi-part solid mandrel be employed, this channel ll may be merely a groove in the outer surface of the mandrel, such groove being somewhat deeper than the helical groove 10.

Having'provided this mandrel, .the helix 5, and the warp wires 1 and 8; the helix 5is first mounted on the mandrel 9 so that the turns 6, 6 and 6 of the helix engage the groove I0 of the mandrel, it being manifest that these turns of the helix will bridge the channel H as illustrated in Fig. 8. At the point where the helical turns bridge this channel it is quite readily possible to spring .apart the crests I and I of the crimps of successive turns 6 and 6 of the helix so as to provide between successive turns and extendin longitudinally of the coils a space 2 (Fig. 8) into which one of the crimped warp wires 1 may be introduced without great difficulty so as to extend longitudinally of the coil. In so interweaving the warp wire 1 with successive weft turns 6, B etc. of the helix, 2. one-and-one weave is preferably employed, and the turns 6, 6 etc. seat themselves in the successive recesses or indentations 2 of the wire 1, while the wire 1 seats itself in the recesses or indentations 2 of each helical turn. When thus arranged the turns 6 and 6 are permitted to spring back to normal position, and since the recesses 2 of the helical turns provide space for the reception of the warp 1, the normal diameter of the helix is not substantially changed by the interweaving of the warps. Having introduced one such wire 1, the helix may be moved circumferentially on the mandrel, substantially a half-revolution, if desired, to present another pair of crests of the helical turns in position above channel I I for separation, and another warp wire I is then introduced, and so on. However, at suitable intervals, in place of the wire I, one of the straight wires 8 may be introduced. Since the wire 8 has no recesses or indentations 2, it is not possible for the turns of the helix to return fully to their normal locations after being sprung apart to permit entry of the wire 8, and the result is that every time a wire 8 is introduced the circumferential length of the helical turns of the helix is thereby slightly decreased. Atthe same time the wire 8 is slightly deflected bythe pressure of the helical turns so that it assumes a very slight undulate form and is thus very firmly held in place by the coils of the'helix. The wires 8 may be intercalated among the wires 1 in any desired order, for instance alternately, one-in-three,'one-in-four, etc.

It will be understood that in introducing the wires 1 and 8,-the turns of the helix are so manip-' ulated that the wires 1 and 8 interweave as warps with successive turns of the helix, to form a true woven structure. The introduction of the straight wires 8, as above noted, tends to decrease the circumferential lengths of the helical turns, thus placing the helical'turns under what may be termed hoop tension and tending to tighten these helical turns very firmly about the wires 1.

After the weaving operation has thus been completed by the interweaving of the wires 1 and 8 with the helical turns, the mandrel 9 may be sprung inwardly so as to permit withdrawal of the completed screen cylinder from the mandrel, or'if the mandrel 9 be'a multi-part rigid mandrel, its parts may be disassembled 'to permit removal of the screen.

Since in this screen structure the helical turns are held inaccurately spaced relation longitudinally of the screen in the indentations of the crimped wires 1, and since the wires "land 8 are held accurately spaced circumferentially by the indentations 2 of the helical turns, it is impossimanner, is shape-retaining, stiff and strong, and

being made of material which is hard, corrosion and erosion resistant, is capable of withstanding the conditions of use such as the impact of high Velocity steam and wide range in temperature,

desired, be

made in lengths substantially longer than the intended filter, and from such lengths of cylindrical material suitable portions may be cut to form the desired individual filters.

Preferably each individual filter is rovided at its opposite ends with a rigid supporting ring in order to give it added strength and to protect it from mechanical injury. As illustrated in Fig. 1, the filter is provided with a top ring-l2 anda bottom ring 13. These rings may be made of any suitable material, but preferably a material which is somewhat malleable, so that it may be bent or deformed as hereafter described. Bronze or some such corrosion-resistant material is desirable for the purpose. As illustrated in Fig. 10, the ring I2 is formed with an outer circumferential wall I 4 and with an inner wall l5 spaced from the wall M to provide the annular channel It. In assembling the screen cylinder with this ring the upper edge of the screen is introduced into the channel 15 and then all or portions of the free edge l8 of the wall l5 are forced over into engagement with the screen material, preferably so as to embrace the upper turn 6 of the helical coil, thereby pinching the screen material against the wall M and providing a mechanical interlock such as permanently to secure the screen and ring together without requiring the use of solder, bracing, welding or the like, all of which have proven unsatisfactory for use in devices of this type.

The lower ring l3 may be substantially identical with the ring 12 as above described, and may be secured to the lower end of the screen in the way above described, but as here illustrated, is provided with a radial flange having openings for the reception of attaching bolts l9.

These bolts secure the screen structure to the lower head 20 of the filter housing 2| forming a part, for example, of a throttle valve casing. The upper ring [2 seats in a suitable recess in the interior of the casing 2|, the latter having the inlet passage 22 which is concentric with the screen or filter, and having the delivery passage or chamber 23 which surrounds the screen and into which the stem is delivered through the interstices or meshes of the screen fabric.

In accordance with a modification of the abovedescribed method of making the seamless cylindrical screen structure, a weft helix of crimped wire is first prepared and placed upon the mandrel 9 as above described, but in this instance the helix has its turn spaced substantially twice as far apart (for a desired mesh size) as they would be in the practice of the previously described method. The crimped warp wires are now merely arranged in parallel relation so as to overlie the turns of the helix (without interweaving them with the turns of the helix) but in such a way that the turns of the helix seat in indentations or recesses of the warp wires. A second helix of crimped wire of slightly greater diameter than the first, and having its turns similarly spaced apart, is now prepared, either by forming it upon a separate mandrel and slipping it endwise over the assembled crimped warp wires and the first helix, or by directly winding the wire about the assembled crimped warp wires to form the helix, this second helix being so arvene between those 'of the first helix, although this second helix is wholly exterior to the assem=-'I bled crimped warp wires. The turns of this second helix are seated in intervening recesses of the crimped warp wires so that the turns of both helices are firmly held in properly spaced rem tion while the crimped warp wiresare likewise held in circumferentially spaced relation by their engagement with the recesses of the helical'tu rn s Straight warp wires are now interposed int-he spaces between adjacent crimped warp wires; and

these straight wires are interwoven withthe turns of the two helices, the straight wires lying-at -the inside of the turns of the first helix and outside of the turns of the second helix. In thus inter;

weaving the straight wires, the latter are sl ig htly deflected from astraight line at the points where, they cross the helical weft turns and thus place the weft turns under stress so that the cr'im'ped warp and weft wires are positively lockedto gether, thus insuring uniformity of mesh Tga rdless of the stresses to which the screen may. be subjected. The structure resulting from this second method is substantially' identical with that" crimped warp wires with the helical weft turns; The second method thusexpedites the produc tion of the article and reduces its cost as compared with the first described method. 3 a

While certain desirable embodiments of the invention have herein been described by wayof example, it is to be understood that the invention is not necessarily limited to this precise *construction, but is to be regarded as broadly 311'10111! sive of any and all modifications which fall within the scope of the appended claims.

I claim:

1. That method of making a seamless cylindrical filter structure which comprises providing a plurality of lengths of transversely crimped, stifliy resilient warp wire, and a plurality of lengths of substantially straight, stifiiy resilient warp wire, providing helically coiled transversely crimped weft wire, so assembling the lengths of crimped warp wire with the helically coiled weft wire that the warp wires extend longitudinally and in substantially parallel, circumferentially spaced relation and with turns of the helically coiled wire seated in recesses in the crimped warp wires, and with the crimped warp wires seated in recesses of the crimped helical weft wire, and introducing lengths of the straight warp wire between adjacent crimped warp wires so that said straight warp wires interweave with successive helical weft wire turns and are slightly deflected from a straight line at the crossing points thereby placing the helical turns under hoop tension.

2. That method of making a seamless cylindrical filter screen which comprises as steps providing a plurality of lengths of transversely crimped, stiflly resilient warp wires and a plurality of lengths of substantially straight, stiffly resilient warp wires, providing a helically coiled weft wire, so assembling the lengths of crimped warp wire with the helically coiled weft wire that the warp wires extend longitudinally and in substantially parallel circumferentially spaced relation and with turns of the helically coiled weft wire seated in recesses in the crimped warp wires, and introducing lengths of the straight warp wire between adjacent crimped warp wires so that said straight warp wires interweave with successive helical Weft ranged, in either instance, that its turns inter-6 wire turns and are slightly deflected from a straight line at the crossing points thereby placingthe helical turns under stress.

3."I'hat method of making a seamless cylindrical filter screen which comprises as steps providing a plurality of lengths of transversely crimped, stiflly resilient warp Wires and a plurality of lengths of substantially straight, stifily resilient warp wires, providing a plurality of helically coiled weft wires, 50 disposing the helically coiled weft wires in coaxial relation that the turns ofvthe respective helices are intercalated, assembling the lengths of crimped warp wire with the helically coiled weft wires in such a Way that the warp wires extend longitudinally and in substantially parallel, circumferentially spaced relationand with the turns of the helical coils seated in recesses in the crimped warp wires, and introducing lengths of the straight warp wire between adjacent crimped warp wires so that said straight warp wires interweave with successive turns of the assembled helical coils and are slightly deflected from a straight line at the crosspoints thereby placingthe helical turns under stress; t

4. ,That method of making a seamless cylindric'al'filter structure which comprises as steps pro-- viding wire which is so contoured as to have reguof greater radial depth than the groove, interweaving with the turns of the wire helix a length ofsa id wire, the interweaving being done at the location of the channel in the mandrel, partially rotating the coil upon the mandrel and interweaving another length of said wire with the helical turns at the location of the channel, repeating such interweaving, thereby to provide a substantially cylindrical open-mesh cylinder, and removing the cylinder from the mandrel.

5. The method as set forth in claim 4 further characterized in that at intervals, during the formation of the cylinder, lengths of normally straight, stifily resilient wire are interwoven as warps.

6. That method of making a seamless cylindrical filter structure which comprises providing a plurality of lengths of transversely crimped, stiflly resilient warp wire and a plurality of lengths of substantially straight, stiflly resilient warp wire, providing a helix of transversely crimped weft wire, so assembling the crimped warp wire with the helix that the warp wires extend'lengthwise of the helix in substantially parallel, circumferentially spaced relation with the turns of the helix seating in recesses of the several crimped warp wires and with the warp wires seated in recesses of the helical wire, disposing a second helix of transversely crimped weft wire so as to embracethe assembled crimped warp wires, with the turns of the second helix seated in intervening recesses of the warp wires, and introducing the substantially straight weft wires into the spaces between adjacent crimped warp wires, the straight wires being interwoven with the turns of the two helices so as to lie inside of the turns of the first helixand to lie outside of the turns of the second helix.

CHARLES L. HARDY. 

